I was at work in my hangar in Fliegerhorst, Germany. Heard it on the radio in the tech supply office. Minutes later we had the work computers on streaming CNN or BBC, and work stopped cold. After a while the CO held a formation to announce officially what we'd all heard, and released us for the day. Most everybody went back to their house or barracks room, turned on the TV, and started packing their gear like zombies - thinking that maybe tomorrow we'd be going to war, maybe even hoping.
Air travel in Europe was unaffected, and our airfield was right under the glide path for Frankfurt International Airport - for weeks, every few minutes a plane would roar overhead and my blood would chill.
Even Germans were New Yorkers that day...by days end, our front gates were piled high with flowers.
2 years later I was at Ground Zero - while on R&R leave from Iraq.